TDI Climate Control: Reheat in Partial Load?

Hello,
'Out of curiosity, I would like to know how the air conditioning system in my car (Seat Ibiza / Córdoba 6L, 1.4 TDI, 59KW, BNV, manual air conditioning) works when I don't run it at full power. Does it mix warm air from the heater while the air conditioning is always running at full capacity, or can the air conditioning system reduce its output to produce less cold air? This would presumably make it much more efficient in partial load operation. There are probably both types of systems, and I'm interested in knowing which one my car has so I can adjust my usage accordingly.'

I'm not familiar with your type of vehicle, but you can easily check it yourself:
An unregulated compressor is engaged to the V-belt using a magnetic clutch. This creates that loud "CLACK" sound accompanied by a drop in engine speed when you turn on the air conditioning. You can easily observe this. Additionally, when the air conditioning is off and the engine is running, you can see that the compressor pulley is rotating, but the compressor shaft and the inner part of the pulley remain stationary.

In a variable-speed centrifugal compressor, the impeller is always running and its performance can be adjusted from 2% to 100%. This adjustment happens gradually, and there is no clicking sound when it starts. The shaft is always rotating.

Greetings.
Guste.

Okay, I'll try that. However, I know that the engine makes a brief 'groaning' sound and then seems to run 'muffled' afterwards when I turn on the air conditioning. This suggests an unregulated compressor. If that's the case, would it be more economical to avoid running the air conditioning in partial load mode, but rather to run it fully cold for 20 minutes, then off for 20 minutes, and then fully cold again, and so on?

Arnie-75 wrote:

If that were the case, it's probably more economical to operate the climate control system not in a partial load mode, but rather to run it fully cold for 20 minutes, then off for 20 minutes, then fully cold again, etc., right?

Besides the economy, you should also take care of your health. I believe it's counterproductive (for your health) to create temperature fluctuations in order to save 0.5 - 1 liter of fuel per 100 km. In Germany, it's not so hot that the air conditioning needs to run 365 days a year. Therefore, I wouldn't want to put extra strain on my health due to the minimal fuel savings.

You might be right. I read a short article on Google yesterday that said a small car can consume up to 5 liters more.
https://www.fabia4fun.de/wbb/index.php/Thread/4494-Klimaanlagen-als-Spritschlucker/

That was also what sparked my interest in climate issues.

Hi.

None of my vehicles (TDI models) showed a significant increase in fuel consumption when using the air conditioning; the increase was in the range of 0.3 to 0.6 liters per 100 kilometers.

If you let the vehicle idle for hours as part of its normal use, you might experience significant increases in fuel consumption, but you should then reconsider the purpose of a VEHICLE.

Therefore, I am joining vag-driver.

Best regards, Rainer.

Okay, then I'll leave it at that.

dieselschrauber wrote:

None of my vehicles (TDI) experienced a significant increase in fuel consumption due to the use of the air conditioning system; the increase was/is in the range of 0.3 - 0.6 liters per 100 km.

The increased energy consumption of the air conditioning system per 100 km is influenced by three factors:
1) On/off compressor vs. rotary compressor. The former offers advantages in terms of energy consumption and, above all, comfort (because the air is not cooled down as much, and therefore is less dry).
2) Outdoor temperature. Higher temperatures result in higher condensation temperatures and a greater demand for cooling capacity.
3) Speed. If the vehicle is driven at an average speed of approximately 100 km/h on the highway, the additional energy consumption per 100 km due to the air conditioning is relatively low. However, if the vehicle is driven in city traffic at an average speed of around 30 km/h with frequent stops at traffic lights, the additional energy consumption per 100 km is significantly higher, because the air conditioning system requires the same amount of power, but fewer kilometers are driven in the same amount of time.

On average, I find Rainer's statements to be relatively accurate for rural areas in Central/Northern Europe. However, in urban traffic, at temperatures of 35-40°C (e.g., a vacation trip through Barcelona), this value will be significantly higher. But even then, turning it off is not an option .